Dental hypersensitivity occurs when dentinal tubules are exposed to external irritation. These tubules become exposed when the enamel covering the crown or cementum or the overlying periodontal tissue covering the root surfaces are lost. This can happen in a variety of ways.

Simply aging can be a factor. "There's an old phrase for aging - you can find it in some of Shakespeare's works - called getting long in the tooth, and it refers to the natural process of gums receding as we get older, " says Tricia Drummand DDS, a member of the Chicago Dental Society.

Sometimes over enthusiastic, over aggressive and improper brushing will lead to gum recession.

Eating and drinking hot and cold food and drinks too close together can aggravate the problem. When you eat or drink something hot the enamel expands quickly and the dentin slowly. Follow this with a quick cold drink and the enamel will contract over the still expanding dentin. Thousands of these episodes will lead to tiny cracks in the enamel.

Over exposer to acids such as indulging in large amounts of oranges, tomatoes or sodas and excessive vomiting in patients with eating disorders will also lead to hypersensitivity.

Whatever the underlying cause, the Chicago Dental Society estimates that sensitive teeth affect as many as forty million Americans with as many as ten million Americans reporting chronic sensitivity problems. Because there are a variety of causes, there are a wide variety of treatment options. A recent study reported in the February issue of the "Journal of the American Dental Association" looked at the efficacy of one of the tools used to help treat hypersensitivity; desensitizing toothpastes.

In this study 230 adults with dental hypersensitivity were randomly assigned to eight weeks of supervised brushing with an assigned toothpaste (Sensitivity Protection Crest; Denquel; Sensodyne SC; and a placebo toothpaste. The examiners used a probe to judge tactile sensitivity, a dental air syringe to detect cold air sensitivity and a subjective questionnaire to indicate participants average level of discomfort/pain. Both desensitizing efficacy and safety were evaluated .

The authors reported that after eight weeks both of the 5 percent potassium nitrate toothpastes ( Sensitivity Protection Crest and Denquel ) were found to be measurably better than the 10 percent Strontium Chloride ( Sensodyne SC) in reducing cold sensitivity and perceived pain. Although it compared better than the placebo for cold sensitivity in four weeks and tactile sensitivity at eight weeks the Sensodyne SC group never reported significant decreases in dentinal sensitivity. The authors concluded that a toothpaste containing both 5 percent potassium nitrate and sodium fluoride for protection against decay would provide safe and effective home therapy for dentinal sensitivity.